Hydroxylamine salts may be represented by the formulae ##STR1## wherein R.sup.1 and R.sup.2 are independently hydrogen or hydrocarbyl groups, X is an anion of an acid, and y is an integer equal to the valence of X. Hydroxylamine salts are compounds which have a variety of applications. For example, hydroxylamine nitrate may be used as a component of liquid propellant and as a reducing agent in photographic operations. In some of these applications it is desirable that the hydroxylamine solution be available in high purity. Furthermore, it is particularly desirable that a solution containing the hydroxylamine salt also contain a reduced amount of acid.
Several methods have been described for manufacturing hydroxylamine salts. In the case of hydroxylamine nitrate, for example, some of these methods include: electrodialysis of hydroxylamine hydrochloride and nitric acid; reaction of hydroxylamine sulfate with barium nitrate; three-step cation exchange process employing hydroxylamine sulfate and nitric acid; and electrolytic reduction of nitric acid. Since these methods do not generally provide hydroxylamine salt solutions of the high purity required for some applications, procedures have been developed to purify the hydroxylamine salt solutions. At present, such solutions are purified using thin film evaporators, vacuum-stripping, or other procedures.
French Patent 2,602,802 is directed to an electrolytic process to directly produce high purity solutions of hydroxylamine nitrate. In particular, a process is described for producing by electrolysis a hydroxylamine nitrate solution in an electrochemical cell containing a cathode compartment, an anode compartment and a separator between the cathode compartment and anode compartment. Said process is characterized in that it includes the following operations: (a) introducing a catholyte, essentially containing an aqueous nitric acid solution, in the cathode compartment; (b) introducing an anolyte solution into the anode compartment; (c) electrolyzing the catholyte to a cathode potential between about 0.5 and 1.4 volts compared to the standard calomel electrode, while keeping the temperature of the reaction to the cathode below about 50.degree. C., in order to produce a hydroxylamine solution; and (d) recovering the hydroxylamine nitrate solution from the cathode compartment.
U.S. Pat. No. 4,521,285 relates to an electrolytic cell and a process for removing the halide or other anion from an organic salt having as general formula A.sup.+ X.sup.-, wherein A.sup.+ is an organic cation and X.sup.- is a halide or other anion. Typical compounds of this type are the hydrohalides of nitrogen gases or other salts or hydrosalts of such bases or compounds notably salts (hydrohalides) of quaternary ammonium bases or of amines or amides. However the process herein contemplated may be applied to the removal of anions, e.g., chloride, which are present as an impurity or in combination with the organic compound.
U.S. Pat. No. 4,645,579 relates to aqueous solutions of hydroxylamine which are prepared from aqueous hydroxylammonium salt solutions by electrodialysis by a method in which the aqueous hydroxylammonium salt solution is fed into the middle zone of an electrolysis cell, which is divided into a cathode zone, an anode zone and a middle zone by means of semipermeable membranes, and is electrolyzed, and the catholyte used is an alkali metal hydroxide solution containing ammonia and/or amines.